setupCache(Configuration taskConf,
String publicCacheSubdir,
String privateCacheSubdir)
Retrieve public distributed cache files into the local cache and updates
the task configuration (which has been passed in via the constructor).

setupCache

Retrieve public distributed cache files into the local cache and updates
the task configuration (which has been passed in via the constructor).
The private distributed cache is just looked at and the paths where the
files/archives should go to is decided here. The actual localization is
done by JobLocalizer.
It is the caller's responsibility to re-write the task configuration XML
file, if necessary.